Recent power issues single phased building. Stepper module replaced by others. Chiller consistently fails on low evap pressure. Can keep running by locking stepper motor to 70%. I can then release back to auto and chiller will run until it shuts down. Upon restarting, fails on low evap again. Calibration needed after board replacement? Any help appreciated
RTHB low evaporator issues
murphman
1 - 7 of 7 Posts
Recent power issues single phased building. Stepper module replaced by others. Chiller consistently fails on low evap pressure. Can keep running by locking stepper motor to 70%. I can then release back to auto and chiller will run until it shuts down. Upon restarting, fails on low evap again. Calibration needed after board replacement? Any help appreciated
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2,088 Posts
No calibration required after swapping stepper modules, put a set of gauges on it and verify all temp sensors don't believe anything the micro tells you.
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8,358 Posts
while it is possible that both chillers failed (or something got fried) during the power outage, it seems quite unlikely that they would both have the exact same issue and solution. i would start looking at the items that are common to both chillers...load, chilled water flow rate, BAS system, etc. The real issue (such as low charge, dirty tubes, etc) could have been riding the edge of faulting out and then a little blip causes it to act up by pushing it over the edge.
posting log sheets with real numbers would cause you to get real help. RTHB, Low Evap Pressure and Power Outage isn't going to get you any more help than telling the doctor you fell and now you hurt.
posting log sheets with real numbers would cause you to get real help. RTHB, Low Evap Pressure and Power Outage isn't going to get you any more help than telling the doctor you fell and now you hurt.
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4,084 Posts
What shuts it down? BAS Schedule? Satisfies setpoint? Other?
I agree with Jay, and would include the secondary chilled water pump (if it's a primary-secondary system), which Jay alluded to with "chilled water flow rate".
What is the discharge superheat and how close is it to the discharge superheat control point??
RTHB will control EXV based on discharge superheat temp and its control point. Check calibration of condenser saturated sensor and discharge temperature sensor.
RTHB will control EXV based on discharge superheat temp and its control point. Check calibration of condenser saturated sensor and discharge temperature sensor.
sounds like evaporator is oil logged
change low refrigerant temp cutout to 28degs
manually control exv to 30% open
run chiller until discharge superheat = exv percentage 30% +- 5
reset low refrigerant temp cutout back to default 32 degs
should recover after 24hrs
change low refrigerant temp cutout to 28degs
manually control exv to 30% open
run chiller until discharge superheat = exv percentage 30% +- 5
reset low refrigerant temp cutout back to default 32 degs
should recover after 24hrs
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